would exif work ? or maybe the binary jhead would work, it gets information 
out fo jpeg files , but they maybe have to be generated only from digital 
cameras i dont know.

>===== Original Message From "Juan Antonio Ruiz Zwollo" <[EMAIL PROTECTED]> 
>Is it possible with PHP to check at what quality/compression a JPEG file has
>been saved? I.e. I have "dummy.jpg" that I got from somewhere else and I
>want to know with what quality it was saved.
>The second Note of the User Contributed Notes on the PHP manual regarding
>the function imagejpeg (http://www.php.net/manual/en/function.imagejpeg.php)
>mentions such a code, and the user hints that he/she is able to read the
>quality of a jpeg, but there is no code given (I have tried contacting the
>user but the comment is quite old):
>"If you call imagecreatefromjpeg and load a jpeg with 75% quality and output
>it with imagejpeg u can specify the new quality for e.g. 90% and u can
>increase quality, but output will look like 75% quality picture with the
>only difference that the new pic is bigger.
>So u should check the source quality before u alter output quality. In most
>cases a quality of 75% is sufficient. For previews i use 50%.
>But i make a check if source quality is lower than my personal output
>quality, i will not chance source quality !
>Hope that helps your Webserver and keeps the traffic low :-)"
>Juan Antonio
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